Re: [PATCH tip/core/rcu 3/4] md/bitmap: Fix list_entry_rcu usage

[Patrick Marlier <patrick.marlier@gmail.com>]

On 09/22/2015 10:50 PM, Paul E. McKenney wrote:
> On Sun, Sep 13, 2015 at 09:10:24AM -0700, Paul E. McKenney wrote:
>> On Sun, Sep 13, 2015 at 12:06:33PM +0200, Patrick Marlier wrote:
>
> [ . . . ]
>
>>> Paul,
>>>
>>> This sounds good to me. It should fix the performance issue (will
>>> check with my benchmark).
>>
>> Thank you, looking forward to seeing the results!
>
> Just following up -- how is the benchmarking going?

Note that in my module I am using the kernel version 3.16.0-31 (I ported 
your change).
Here the results of my benchmark that tests rculist in the case of read 
only.

# 1st column : The number of threads
# 2nd : ops/s the original version
# 3rd : ops/s your version with lockless_dereference
1 883923 1747554
2 1741441 3543062
3 2462360 5103647
4 3437273 7176608
6 5155803 9812348
8 6718111 13330050
10 8519227 17458294
12 9773632 20298897
14 11555198 23191424
16 11643264 25125712

I get same performance with my patch.
So indeed it fixes the performance problem I was seeing.

Thanks a lot!
--
Pat